The present invention relates to improvements in rolls for use in calenders and like machines. More particularly, the invention relates to improvements in rolls of the type disclosed, for example, in commonly owned U.S. Pat. No. 4,520,723 granted June 4, 1985 to Pav and Wenzel. Rolls of the type to which the present invention pertains can be utilized in calenders, in glazing machines, in press sections of papermaking machines, in other pulp processing machines, in printing presses, in rolling mills for steel, plastic and/or other materials, and as pulleys and/or deflectors in conveyor systems for sieves, webs of textile material and the like.
The patent to Pav and Wenzel discloses a roll wherein a shell rotatably surrounds and is movable radially with reference to a stationary carrier in the form of a beam which is non-rotatably mounted in a frame. The shell confines one or more rows of hydrostatic supporting elements which can change the shape of the shell by reacting against the carrier. The end portions of the shell carry antifriction bearings which surround sleeves, and each such sleeve is non-rotatably but vertically movably mounted on a stub of the carrier. The means for holding the sleeves against rotation with the shell, i.e., relative to the respective stubs of the carrier, includes rollers which are received between vertical guide members on the carrier.
German Auslegeschrift No. 22 54 392 of Biondetti discloses a modified roll wherein the sleeves are formed with window-like cutouts flanked by parallel surfaces which engage flats on the respective stubs of the carrier. A similar roll is disclosed in German Auslegeschrift No. 28 26 316 of Biondetti.
A drawback of heretofore proposed devices which serve to prevent the sleeves from rotating with the shell, while permitting the sleeves to move back and forth relative to the carrier, is that the hydrostatic supporting elements which operate between the shell and the carrier must overcome pronounced friction between the carrier and the parts which hold the sleeves against rotation on the carrier. The frictional engagement between the sleeves and the carrier is especially pronounced if the sleeves have windows flanked by lateral surfaces which are in large-area contact with adjacent flats of the carrier. Thus, even a minor tilting of the sleeves can entail a jamming so that the shell is held against radial movement with reference to the carrier or can be shifted only in response to the application of very large disengaging forces which are likely to damage certain parts of the roll. The provision of rollers which are caused to travel in grooves defined by guide rails or by like parts brings about a substantial reduction of forces which are necessary to overcome friction between the rollers and the guide means on the carrier. However, the rollers are normally in a mere linear contact with the adjacent guide means; this can entail the development of pronounced Hertzian stresses and a flattening or facetting of the peripheral surfaces of the rollers with attendant increase of friction between the thus deformed rollers and the guide means on the carrier. Since the extent of such frictional engagement is unpredictable and since such frictional engagement varies as a function of several parameters, any friction between the sleeves and the carrier can diversely affect the degree of accuracy with which the orientation and/or the shape of the shell is adjusted relative to the carrier and/or with reference to one or more neighboring rolls.